HETEROGENEOUS REACTION PROCESSES IN METAL COMBUSTION.
VIRGINIA UNIV CHARLOTTESVILLE
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This paper deals primarily with the case of vapor-phase burning. Heterogeneous reaction of metal vapor and oxygen and possibly of volatile oxide species may take place at the surface of growing oxide smoke particles, in competition with homogeneous gas-phase reaction followed by condensation. The relative importance of the heterogeneous and homogeneous reaction paths is currently the subject of some speculation and controversy. In this connection, a knowledge of the collision efficiency of the heterogeneous reaction was of considerable interest. For the Mg - O2 reaction, an average collision efficiency of 0.075 was previously derived but this value cannot be regarded as very reliable. Results obtained by a recently developed method indicate larger values, probably exceeding 0.3. The mechanism of the reaction of metal vapor and oxygen at the oxide surface is unknown. However, from analogy with chemisorption and catalysis at oxide surfaces, it is found that electron transfer plays an important role, and, under some conditions, may become rate-controlling. Observations of luminescence and of anomalous electron emission during reaction of Mg vapor and oxygen at the oxide surface have provided evidence for electronic excitation in the oxide layer.
- Physical Chemistry
- Combustion and Ignition